MILAN, June 19 (Reuters) - Italian gas group Snam is in exclusive talks with EDF's Italian unit Edison to buy a stake in a liquefied natural gas terminal in northern Italy as part of plans to develop its LNG business, two sources said.

Snam, controlled by state lender Cassa Depositi e Prestiti, is looking to buy Edison's 7.3 percent stake in Terminale LNG Adriatico and the gas pipeline that connects it to Italy's gas transmission backbone, the sources said.

Adriatic LNG, which has a capacity of 8 billion cubic metres per year, is 70.7 percent owned by ExxonMobil and 22 percent by Qatar Petroleum. Exxon and Qatar have a pre-emption right on Edison's stake.

Snam said it did not comment on market speculation.

Edison said in June talks were under way to sell the stake and pipeline as well as two offices in Milan hosting its headquarters.

"The idea is to wrap up the sale in the first half of July, though some slippage can't be ruled out," one of the sources said, adding Banca IMI was advising Edison on the deal.

Snam, which makes most of its money from gas transmission, is looking to play a leading role in integrating Europe's grids and making Italy a European gas hub.

In its March business plan it said it would be looking at opportunities to grow its LNG infrastructure business.

According to Italian newspaper Il Sole 24 Ore, Edison's stake in the Adriatic LNG platform has a book value of 159 million euros ($177 million) while the pipeline has a book value of 32 million euros.

It was not possible to confirm these values but one of the sources said if a deal went through it would be for a higher price.